PIN number much appreciated, being in credit (7)

'pin' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I don't see?

'number much appreciated being in credit' is the wordplay.
'number' becomes 'n' (n can represent any number).
'much appreciated' becomes 'ta' (both are ways of saying thank you).
'being in' indicates putting letters inside.
'credit' becomes 'tick' (on tick can mean purchased on credit).
'n'+'ta'='nta'
'nta' put within 'tick' is 'TINTACK'.

Can you help me to learn more?